I have to exit China once. Can i just stay a half a day in Hongkong and then enter again?

I have a german passport with a 2 entry L visa. I know i have to exit mainland once but i dont necessary want to stay a whole day in Hongkong. Is it possible to exit for a few hours and then reenter? If yes what adress should i put in the entry slip for the hongkong registration at the border? Because i wouldnt actually stay in a Hotel.